1. Technical Field
The present invention generally relates to a particle detector and a method of using the same. More particularly, the present invention generally relates to a system used to detect particles by using an electrowetting microlens and a method of detecting particles using the same.
A claim of priority is made to Korean Patent Application No. 2004-0038060, filed May 28, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety.
2. Discussion of Related Art
Developments in semiconductor devices are increasing almost on a daily basis. The development of ultra highly integrated semiconductor devices has advanced the electronic communication industry and the multimedia field. The development of the semiconductor devices is an aggregate of circuit design technology, equipment technology, and process technology.
Manufacturing processes for a semiconductor device consist of photo-lithography, etching, ion implantation, thin film formation, and metal wiring. Among these processes, a pattern formation by a photo-lithography process is a key process in the manufacture of the ultra highly integrated semiconductor devices. The photo-lithography process is divided into a coating step, an exposure step, and a development step. The exposure step and equipment used for the exposure step are very important in the photo-lithography process.
During the exposure step, a substrate is coated with a photo-resist, a soft bake is performed on the substrate, and a temporary phase is formed on the photo-resist.
To perform the exposure step, an exposure device capable of transferring a circuit pattern onto a substrate is used. Recently, a projection exposure device has been used to transfer a photo-mask pattern or reticle onto a substrate such as a semiconductor substrate or a glass plate by coating a photosensitive material onto a surface of the substrate.
However if particles, such as dust, contaminate the surface of the reticle, the photo-lithography process can be degraded, impairing the proper formation of circuit patterns on a substrate.
Under some circumstances, a pellicle is used to protect the circuit pattern formed on the reticle. The pellicle is a passivation layer that prevents contaminates such as dust from reaching the reticle. That is, the pellicle functions to protect a surface of reticle from air dust during a photo-lithography process. The pellicle is generally made of thin and transparent nitro-cellulose material.
However, when a pellicle is employed, particles can also adhere to the pellicle, thereby degrading the exposure process and impairing the proper formation of circuit patterning on a substrate.
In a conventional exposure device, a scanner using a light emitting diode (LED) laser is used to detect particles on the upper and lower side surfaces of a reticle, or a pellicle formed on the reticle.
FIG. 1 is a schematic view illustrating a detecting operation of a conventional particle detector.
As shown in FIG. 1, the conventional particle detector includes a light emitting device 50, a light receiving device 60, and a detecting member (not shown). Light emitting device 50 transmits light 40 to a reticle 10 or a pellicle 20, if applicable. Light receiving device 60 receives light 40 after it has been reflected by a surface of reticle 10 or pellicle 20. The detecting member analyzes light 40 and detects whether there are particles on the surface of reticle 10 or pellicle 20.
In detail, if light 40 emitted by light emitting device 50 is transmitted to a surface 22 of reticle 10 or pellicle 20 at a predetermined angle, and no particles are present, light 40 reflected by the same angle as the transmitted angle is received by light receiving device 60. However, when particles are present, light 40 transmitted by light emitting device 50 scatters, and only a portion of light 40 is received by light receiving device 60. Accordingly, the received light 40 is analyzed, and a determination is made as to whether particles are on present on reticle 10 or pellicle 20.
FIG. 2 is a schematic view illustrating a detecting operation of the conventional particle detector shown in of FIG. 1.
Particle detection is sometimes performed, even though pellicle 20 is not completely adhered to reticle 10, or a thickness of pellicle 20 is not uniform.
In the aforementioned cases, since an incident angle of light maintains a constant value based on the surface of pellicle 20 having a relative small thickness, only particles present at a surface of pellicle 20 are accurately detected. In contrast, it is difficult to accurately detect particles on a surface 12 of a reticle 10 without a pellicle, or on a surface 32 of a pellicle 30 having a relative larger thickness.
In the conventional particle detector, an incident angle of light should be changed as a function of the presence or the thickness of a pellicle. However, it is impossible for the conventional particle detector to adjust the incident angle of light. Therefore, particle detection accuracy varies significantly based on the type or the presence of the pellicle.